1. Field of the Invention
This invention relates to absorbent material based on clay minerals.
2. Brief Description of the Prior Art
Clay minerals in particulate form are commonly used to absorb liquids. For such use the clay is mined or quarried and the resulting so-called raw clod is crushed to produce for example, largest particles of the size order of about 1-3 cm, is dried if necessary to render it capable of absorbing a reasonable quantity of liquid, for example to a water content of not more than 20% by weight and preferably about 5% to 15% by weight, and is screened, while usually also involves some breakdown of the clay particles which have become physically weaker during the drying process, to give a final product in about the 710 microns to 4 mm size range or thereabouts. Reference hereafter to a material having a specific size range is to the majority and preferably at least 75% by weight of the material being in the form of particles having sizes within that range unless otherwise stated. The size ranges stated are, where appropriate, conversions into nominal aperture widths in metric units of British Standard mesh size ranges (see British Standard 410.1962) and should be interpreted accordingly.
The resulting particulate clay mineral product is useful for absorbing aqueous liquids a major use being as a pet for example cat litter. For such a use the liquid capacity of the absorbent is of the greatest importance if a produce is to be acceptable to the purchaser since it determines the frequency with which the absorbent, in use, must be changed for fresh material.